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Aug'QZl, 1923. 1.465298 G. CRISSON ET AL CORD CIRCUIT REPEATEH FOR USE BETWEEN FOUR-WIRE AND TWO-WIRE CIRCUITS Filed April 15 1921 gwuemtow 6: Unison 030 Patented Aug. 21, 1923.

UNITED STATES GEORGE CRISSON, OF HACKENSJ PATENT OFFICE.

BRIGHTON, NEW YORK, ASSIG'NOBS T0 AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A CORPORATION 03? NEW YORK.

CORD-CIRCUIT REPEATER FOR USE BETWEEN FOUE NIEE AND TWO-WIRE CIRCUITS.

Application filed April 15,

.1 stwecn i our and Twodvire Circuits, ot whicl'i the lowing is a s] eci[ication.

This invention relates to transmission. lines and more particularly to improved arrangements tor establishii connections be tween two transmission lint one or both oi? which are of the well known tour-wire type) It is at times desirable to utilize twoway repeater circuit in a cxmnection of this type. When this is the case it is necessary to provide a good impedanrr balance at the end of the tour-wire circuit and also at the line and network terminals oi the repeater. in order to obtain satisfactory trr sion. Ordinarily this might be. accomplished by providing two special balancing networts and sets oi equipment in the terminal arrangements oi the tourwire circuit one to match. the impedance ot the circuit and one to match the impedance ot the repeater. These would be oi complex construction and expensive in installation. With the arrangements ot this invention, however, a high degree o'l' balance may be provided in the repeater without he use oi" any such special networks- There is furthermore in accordance with the arrangen'icuts of this invention, incorporated in. the circuit arrangements means .vl'iereby, vhen a coin nection of this type is completed through acord circuit repeater, the normal circuit equivalent and repeater gain is preserved. Other features and purposes of the invention will appear more fully from the detailed description hercinatter given.

The invention may be more tully unth rstoodfrom the tollowino; alescrirftion togetln er with the accompanying drawing in the Figures 1 andQ of which are illustrated a preferred embodiment of the arrangements of the invention. In Fig. '1. is shown a circuit diagram of the arrangements of the invention, while in Fig. 2 is shown a circuit diagram illustrating in schematic form. the principles of operation ot the invention.

The circuit of Fig. 1 shows the terminal Serial No. 461,643.

and a cord circuit repeater for establishing connections between said circuits. The fourwire circuit is well known in the art and might be of the type illustrated in the ll. S. vPatent llo. 1,352,786, dated September 14, 1920, to t}, A. Campbell, or other types, such as are used tor transmission of carrier currents. It includes an incoming line L and an a iing line L both of whic hare ed nnh the windings of: the hybrid coil 1. The windings ot the hybrid coil 1 are normally connected over conductors 18 and 19 to tile acl: J andare also connected to the usual type of balancing network N There is also provided a relay 2 whereby the snY, AND .anrnun r. ROSE, or WEST windings oi hybrid coil 1. may be disconneeted from networl'c N and may be connected over conductors 3 and 1 to the contacts otjack il The relay 2 is controlled ovelr cTonduetor connected to the sleeve of ZLL I (I... iilso piovided and may be associated with conductors 1S and 19 and 3 and 4 by the operation of the relays 1 1, 15, 16 and 17 for purpose which will be pointed out later.

The cord circuit repeater terminatesin the twin plugs P P and P P which are adapted to cooperate with the jacks J J ot the tour-wire circuit and the jacks J J, or". the two-wire line respectively. The contacts ot plugs l? l. are connected to the opposite sides of windings oil. the hybrid coil 6, while the contacts oi plugs P and P are connected to the opposite sides of windings oil the hybrid coil 9. The plugs P and P are commonly known as the line plugs while the plugs P and P are commonly known as network plugs. In the cord circuit repeater would be the repeater elements 10 and 11. These repeater elements might be any suitable term of elm-way repeater. such for example as the well-known vacuum. bulb aniplilier. and are accordingly herein illustrated in schematic term only. The cord circuit repeater circuit is well lrnown in the art and no further description thereof will be given. The two-wire line circuit L terminates in the jack J, and there isalso provided a network jack J, with which is associated the usual type of network N For balancing line L 7 The artificial lines 12 and-13 are When a connection is to be established through the cord circuit repeater the plugs P and P are inserted in acks J and J and plugs P and P are inserted in 1acks J and J The "following circuit will then conductor '5, sleeve contacts of jack i, plug P sleeve conductor or plug P to battery and ground. The closing oi' this circuit will operate relay 2 which will disconnect the network from the hybrid windings l and connect these windings over conductors 3 and 4 to the ack J and thence over conductors 7 and 8 to windings of the hybrid coil 6. This causes the cord circuit repeater .to act efi'ectively as a t-eininal four-wire repeater. In other words it amounts to practically putting the repeaters 10 and 11. directly .into the circuits la and L respectively by coupling the one-way circuits of the tour-wire line with the one-way circuits of the repeater through an intermediate toun j wire circuit arrangement which includes the hybrid C01l windings.

The principles of operation of the arrangements may be more clearly understood from Fig.2 in which there is shown the circuit arrangement resulting upon the operation of relay 2. Similar reference characters have been utilized to denote like parts with respect to Fig. in Fig. 2 the heavy arrows show the direction the current would take when transmission takes place from circuit L to circuit L and the dotted arrows show the direction the current would take when transmission takes place from circuit l to circuit L It will be seen that current transmitted from circuit L to circuit L will be transmitted over a circuit including conductors 1S and i and one of the windings o'l each of the hybrid coils l and 6 and also over conductors l9 anc 3 and the ren'iaining win dings of the coils. I These windings in this cormection act simply as transformers and the current will not affect circuits L and L as the conductors of these circuits as connected to points of equal potential. Current transmitted from circuit L to circuit L will be transmitted over a balanced phantom circuit including conductors l9 and 3 and windings of the coils on one side and conductors 1S andel and windings ot the coils on the other side. Accordingly the current transmitted over these phantom circuits will not allect the windings of the coils which are directly connected to circuits L and and will not disturb the transmission thereover.

It is pointed out that, when a connection of the above character is set up, the usual division of energy does not take place in the hybrid coils 1 and (3 since all the energy put out by one coil is transmitted to the other instead of wastinghalf of is in a net Work and all ot the energy received by the second coil is sent into one of the one-way 1,4.e5,2ee

circuits of the repeater instead of being diruled equally between both such circuits. This has the ell ect of reducing the ei'lective transmission equivalent of the four-wire circuit by about three inileunits. and also ncreases the repeater gain by about three leamits, thus altering the transmission equivalent by about six mile-units from the normal. In order to compensate for this alteration and to preserve the normal transmission qualities of the circuit when a connection 01 this type is set up, the artificial lines lQ and and the relays la, 15, it and 1? are provided. The artificial line 12 is associated with conductors 18 and 19, but is normally disconnected from them and the artificial line l-l is associated with conductors 3 and a, but is normally disconnected from them. When a circuit connection is set up through the cord circuit repeater, these relays are operated over the sleeve circuits oi? jack J, and plug P and the artiiicial lines and 13 are then directly included in coinluctors i8, i9 and 3, a, respectively. This will conjipensate for any alterations in the normal transmission qualities of the circuit due to the unusual division oi the energy and will cause the tansmission to remain substantially constant.

ll hile the invention has been disclosed in certain specific arrangements which are doomed desirable it is understood that it is capable oi? einlmdinient in many and widely varied forms without departing from the spirit of the invention, defined in the appended claims; for example the invention might be utilized to interconnect two fourwire circuits without the use of an intermediate repeater, or the invention might be utilized in a connection between two circuits one of which would include apparatus for sending and receivingsignaling currents of carrier frequency.

lVhat is claimed. is:

1. A four-wire circuit including two one way lines for transmission in opposite directio us terminating at a station in a hybrid coil, a line jack and a network jack at said station, two. of the terminals of windings of said. hybrid coil being connected to said line jack and two of theterminals oi said windings being connected to a balancing network, a repeater cord circuit at saic. station including a line plug and a network plug and a hybrid coil, two of the terminals of windings of said hybrid coil being con-- nected to said line plug and two of the terminals of said windings being connected to said network plug, and means in said four-wire circuit operative when said line plug and network plug are inserted in d line jack and network jack respectively whereby two of the terminals of windings of said first mentioned hybrid coil may be disconnected from said balancing network til normally connected thereto and may be connected to said network jack.

2. A four-wire circuit including two oneway lines for transmission in opposite directions terminating at a station in a hybrid coil, a line jack and a network jack at said station, two of the terminals of windings of said hybrid coil being connected to said line jack and two of the terminals of said windings being connected to a balancing network, a repeater cord circuit at said station including a line plug and a network plug and a hybrid coil, two of the terminals of windings of said hybrid coil being connected to said line plug and two of the terminals of said windings being connected to said network plug, means in said four wire circuit operative when said plugs are inserted in said jacks whereby two of the terminals of windings of said first mentioned hybrid coil may be disconnected from said balancing network and may be connected to said network jack, compensating artificial lines associated with said jacks, and means operative when said plugs are inserted in said jacks for connecting said compensating artificial lines in circuit with said jacks.

3. A circuit arrangement including two one-way lines for transmission in opposite directions, said two one-way lines terminating in a hybrid coil, a two-way repeater circuit, means for connecting together the two-wire line terminals of said hybrid coil and said repeater circuit, and means for connecting together the network terminals of said hybrid coil and said repeater circuit.

4:. A circuit arrangement including two one-way lines for transmission in opposite directions, said two one-way lines terminating in a hybrid coil, a two-way repeater circuit, means for connecting together the two-wire line terminals of said hybrid coil and said repeater circuit, means for connecting together the network terminals of said hybrid coil and said repeater circuit, and compensating artificial lines in each of said connecting means.

5. A circuit arrangement including two one-way lines for transmission in opposite directions, said two one-way lines terminating in a hybrid coil having line and network terminals, a second circuit arrangement including two one-way lines for transmission in opposite directions, said two oneway lines terminating in a hybrid coil having line and network terminals, and means for connecting together the line terminals of each of said hybrid coils and for connecting together the network terminals oi each of said hybrid coils.

In testimony whereof, we have signed our names to this specification this 13th day of April 1921.

GEORGE CRISSON. ARTHUR F. ROSE. 

